Some electronic devices use touch-sense devices, such as touch screens, touch pads, sliders, or buttons, to provide input. A button provides a binary indication (on or off). A slider provides a one-dimensional indication (a value in a range between a minimum value and a maximum value). A touch screen (or touch pad) provides a two-dimensional indication (both an X dimension value and a Y dimension value). Some touch screens are implemented using approaches equivalent to that of two orthogonal sliders. Other touch screens use an array of sensors, such as an array of capacitive sensors.
Some touch-sense devices, such as a button, use mechanical switches. Some touch-sense devices use other techniques, such as a slider which acts as a resistive divider around a point of touch, enabling a calculation of a location of the point of touch by measurement of resistance. Some touch-sense devices use capacitive techniques to measure the location of the point of touch. Some touch-screen devices use current sensing (such as measuring, at each of the four corners of the screen, current drawn through a finger touching the screen), or acoustical techniques (such as surface acoustic wave techniques).
Some existing touch-sensing devices, such as some button devices, incorporate a mechanical layer having switches below a capacitance-sensing layer. A light press triggers only the capacitance-sensing layer, while a strong press also triggers the switches, thus enabling a light press to be distinguished from a strong press, and enabling the touch-sensing devices to report additional information (not solely an occurrence of a press, but also a type of the press). Approaches such as this, however, are limited in scalability because of the use of mechanical switches (which are generally poorer at fine-grained position detection), and are also expensive due to the need to integrate two different types of sensors (such as mechanical and capacitance-sensing).